Half the page I was editing (created 2003) has disappeared

I have been revising the story of my life, a bit at a time. It was annoying today to discover that I would have to use the new online Sitebuilder Plus. It was disillusioning to discover some time later that the first part of the story - a l ot of work with many images, has disappeared.

Can't some editor help recover this for me? Is it on my files on my Homestead on my home computer? Isn't this one reason for having the Sitebuilder to download?